I, for one, love playing soccer.
Anywho, do you play lacrosse in competition? And if you do, then don't you play outside at all times?
Indoor's have walls, the can prove to be massive obstacles. You will probably get used to the indoors and start playing lacrosse outside like you would inside, if you get what I mean.
As for the soccer players... Ask them kindly if you can use the gym for certain days of the week. Don't flame at them, it'll only make the situation worse
Hope everything works out mate.